1. Field of the Invention
The invention relates to a process and installation for the production of a steel strip having a thickness of 2 to 25 mm by the casting of a steel strand having a thickness of less than 100 mm, followed by the rolling out of the steel with utilization of the casting heat, the cast strand being subjected in at least one pass to a change in cross-section producing a stretching.
2. Discussion of Prior Art
The idea of producing strips or sheets by rolling a cast strand directly from the casting heat is known. However, such processes have hitherto been used exclusively for low-melting metals, such as brass, copper and aluminium.
The processes used in practice for the production of hot-rolled steel strip having a thickness as well of less than 20 mm as a rule start from a continuously cast slab which after complete solidification is reheated to rolling temperature, reduced in thickness in a number of passes, and rolled out into a strip. For this purpose up to nine roll stands are required, due to the considerable thickness of the slabs used. Installations for the use of such a process call for heavy investment costs, since they require on the one hand a correspondingly large continuous casting installation, and on the other hand demand a multi-roll-stand hot-rolled strip rolling train whose roughing stands must be of suitable compact construction, due to the thickness of the slabs to be rolled out.
To reduce this expense, it has already been suggested to start from cast preliminary strip having a thickness of 20 to 65 mm in the production of thin strips (German OS No. 32 41 745). The preliminary strip is produced in the continuous casting installation in the conventional manner, being cooled and after complete solidification subdivided into pieces of suitable length and wound into a coil. In preparation for the subsequent rolling out to form the thin strip, the coil is thermally treated in an intermediate storage furnace and adjusted to a uniform temperature. Rolling out is performed in a number of passes. The expense of rolling thin strips still remains high, due to the required intermediate storage furnace and the large number of roll stands.